2D compact reactive beam forming network for automotive radars

ABSTRACT

A radar system includes a plurality of radiating elements configured to radiate electromagnetic energy and a plurality of feed waveguides defining a common plane and configured to guide electromagnetic energy to the plurality of radiating elements. The radar system also includes a plurality of waveguides arranged as a dividing network. The dividing network is also configured to split the electromagnetic energy from the source among the plurality of feed waveguides, such that each feed waveguide receives a respective portion of the electromagnetic energy. Additionally, the dividing network is configured to adjust a phase of the electromagnetic energy received by each waveguide. The splitting and adjusting of the dividing network may be based on differences in width between the waveguides of the dividing network and the feed waveguides. The dividing network of waveguides is located in the common plane of the feed waveguides.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. patent application Ser.No. 14/977,964, filed on Dec. 22, 2015, the entire contents of which areherein incorporated by reference.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Radio detection and ranging (RADAR) systems can be used to activelyestimate distances to environmental features by emitting radio signalsand detecting returning reflected signals. Distances to radio-reflectivefeatures can be determined according to the time delay betweentransmission and reception. The radar system can emit a signal thatvaries in frequency over time, such as a signal with a time-varyingfrequency ramp, and then relate the difference in frequency between theemitted signal and the reflected signal to a range estimate. Somesystems may also estimate relative motion of reflective objects based onDoppler frequency shifts in the received reflected signals. Directionalantennas can be used for the transmission and/or reception of signals toassociate each range estimate with a bearing. More generally,directional antennas can also be used to focus radiated energy on agiven field of view of interest. Combining the measured distances andthe directional information allows for the surrounding environmentfeatures to be mapped. The radar sensor can thus be used, for instance,by an autonomous vehicle control system to avoid obstacles indicated bythe sensor information.

Some example automotive radar systems may be configured to operate at anelectromagnetic wave frequency of 77 Giga-Hertz (GHz), which correspondsto millimeter (mm) electromagnetic wave length (e.g., 3.9 mm for 77GHz). These radar systems may use antennas that can focus the radiatedenergy into tight beams in order to enable the radar system to measurean environment with high accuracy, such as an environment around anautonomous vehicle. Such antennas may be compact (typically withrectangular form factors; e.g., 1.3 inches high by 2.5 inches wide),efficient (i.e., there should be little 77 GHz energy lost to heat inthe antenna, or reflected back into the transmitter electronics), andcheap and easy to manufacture.

In some scenarios, efficiency may be difficult to balance with cheap andeasy manufacture. Some cheap and easy to manufacture options may involveintegrating an antenna into a circuit board (e.g., with a “series-fedpatch array”), which is used by many off-the-shelf automotive radars.However, such antennas may lose much of their energy into heating up thesubstrate of the circuit board. Antennas with the lowest loss mayinclude all-metal designs, but typical all-metal antennas, such asslotted waveguide arrays, can be difficult to manufacture with the smallgeometries compatible with 77 GHz operation.

SUMMARY

In one aspect, the present application describes a radar system. Theradar system includes a plurality of radiating elements, where theradiating elements are configured to radiate electromagnetic energy. Theradar system also includes a plurality of feed waveguides, where eachfeed waveguide is configured to guide electromagnetic energy to at leastone of the plurality of radiating elements such that each radiatingelement corresponds to one of the plurality of feed waveguides. Eachfeed waveguide has a height and width dimension in common with eachother feed waveguide, and the plurality of feed waveguides is arrangedsuch that centers of the heights of the feed waveguides are located in acommon plane. The radar system also includes a plurality of waveguidesarranged as a dividing network. The dividing network is configured toreceive electromagnetic energy from a source. The dividing network isalso configured to split the electromagnetic energy from the sourceamong the plurality of feed waveguides, such that each feed waveguidereceives a respective portion of the electromagnetic energy from thesource. Additionally, the dividing network is configured to adjust aphase of the electromagnetic energy received by each waveguide. Thesplitting and adjusting of the dividing network may be based in partbased on differences in width between the waveguides of the dividingnetwork and the feed waveguides and the dividing network of waveguidesis located in the common plane of the feed waveguides.

In another aspect, the present application describes a method ofradiating a radar signal. The method includes receiving electromagneticenergy from a source. The method also includes splitting theelectromagnetic energy from the source as a divided signal among aplurality of feed waveguides by a dividing network, such that each feedwaveguide receives a respective portion of the electromagnetic energyfrom the source. Additionally, the method includes for each of theplurality of feed waveguides, adjusting a phase of the electromagneticenergy received by each feed waveguide by the dividing network. Also,the method includes for each of the plurality of feed waveguides,coupling electromagnetic energy to a plurality of radiating elementscoupled to the feed waveguide. Further, the method includes radiatingelectromagnetic energy by the plurality of radiating elements coupled tothe plurality of feed waveguides. The splitting and adjusting of themethod are based in part based on differences in width between thewaveguides of the dividing network and the feed waveguides, and thedividing network is located in a common plane of the feed waveguides.

In yet another aspect, the present application describes a radar unit.The radar unit includes a plurality of feed waveguides located in acommon plane, each feed waveguide configured to guide electromagneticenergy from an end of the feed waveguide to at least one radiatingelement coupled to the feed waveguide. The radar unit also includes awaveguide source. Further, the radar unit also includes a dividingnetwork comprising a plurality of waveguides, where the dividing networkis located in the common plane. The dividing network is configured toreceive electromagnetic energy from the source. The dividing network isalso configured to split the electromagnetic energy from the sourceamong the plurality of feed waveguides, such that each feed waveguidereceives a respective portion of the electromagnetic energy from thesource. The dividing network is further configured to adjust a phase ofthe electromagnetic energy received by each feed waveguide. Thesplitting and adjusting of the dividing network are based in part basedon differences in width between the waveguides of the dividing networkand the feed waveguides, and the dividing network comprises reactiveelements and no absorption load elements.

In still another aspect, a system is provided that includes a means forradiating electromagnetic energy. The system includes means forreceiving electromagnetic energy from a source means. The system alsoincludes means for splitting the electromagnetic energy from the sourcemeans as a divided signal among the plurality of feed guide means by adividing means, such that each feed guide means receives a respectiveportion of the electromagnetic energy from the source means.Additionally, the system includes for each of the plurality of feedwaveguides, means for adjusting a phase of the electromagnetic energyreceived by each feed guide means by the dividing means. Also, thesystem includes for each of the plurality of feed waveguides, means forcoupling electromagnetic energy to a plurality of radiating meanscoupled to the feed guide means. Further, the system includes means forradiating electromagnetic energy by the plurality of radiating meanscoupled to the plurality of feed guide means. The means for splittingand means for adjusting of the system are based in part based ondifferences in width between the guide means of the dividing mean andthe feed guides means, and the dividing mans is located in the commonplane of the feed guide means.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flowchart of an example method to radiate electromagneticenergy.

FIG. 2A illustrates a first layer of an example antenna, in accordancewith an example embodiment.

FIG. 2B illustrates a second layer of an example antenna, in accordancewith an example embodiment.

FIG. 2C illustrates an assembled views of an example antenna, inaccordance with an example embodiment

FIG. 2D illustrates an assembled views of an example antenna, inaccordance with an example embodiment.

FIG. 2E illustrates conceptual waveguide channels formed inside anassembled example antenna, in accordance with an example embodiment.

FIG. 3A illustrates a network of wave-dividing channels of an exampleantenna, in accordance with an example embodiment.

FIG. 3B illustrates an alternate view of the network of wave-dividingchannels of FIG. 3A, in accordance with an example embodiment.

FIG. 4A illustrates an example two-dimensional beamforming network, inaccordance with an example embodiment.

FIG. 4B illustrates an example three-dimensional beamforming network, inaccordance with an example embodiment, showing power dividing section424 and the phase adjustment lens 426.

FIG. 4C illustrates an example three-dimensional beamforming network, inaccordance with an example embodiment feeding a 5×10 array of OEWGarrays.

FIG. 4D illustrates an example three-dimensional beamforming networkwith short wall coupling, in accordance with an example embodiment.

FIG. 4E illustrates an example three-dimensional beamforming networkwith short wall coupling, in accordance with an example embodiment.

FIG. 4F illustrates an example short wall coupler, in accordance with anexample embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying figures, which form a part hereof. In the figures, similarsymbols typically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, figures, and claims are not meant to be limiting. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the scope of the subject matter presented herein. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

The following detailed description discloses an apparatus for a “dualopen-ended waveguide” (DOEWG) antenna for a radar system for anautonomous vehicle, for instance, and a method for fabricating such anantenna. In some examples, the term “DOEWG” may refer herein to a shortsection of a horizontal waveguide channel plus a vertical channel thatsplits into two parts, where each of the two parts of the verticalchannel includes an output port configured to radiate at least a portionof electromagnetic waves that enter the antenna.

An example DOEWG antenna may comprise, for example, two metal layers(e.g., aluminum plates) that can be machined with computer numericalcontrol (CNC), aligned properly, and joined together. The first metallayer may include a first half of an input waveguide channel, where thefirst half of the first waveguide channel includes an input port thatmay be configured to receive electromagnetic waves (e.g., 77 GHzmillimeter waves) into the first waveguide channel. The first metallayer may also include a first half of a plurality of wave-dividingchannels. The plurality of wave-dividing channels may comprise a networkof channels that branch out from the input waveguide channel and thatmay be configured to receive the electromagnetic waves from the inputwaveguide channel, divide the electromagnetic waves into a plurality ofportions of electromagnetic waves (i.e., power dividers), and propagaterespective portions of electromagnetic waves to respectivewave-radiating channels of a plurality of wave-radiating channels. Thetwo metal layers may be called a split block construction.

In various examples, the power dividing elements of the DOEWG antennamay be a three-dimensional dividing network of waveguides. Thethree-dimensional dividing network of waveguides may use waveguidegeometry to divide power. For example, the feed waveguides may have apredetermined height and width. The predetermined height and width maybe based on a frequency of operation of the radar unit. Thethree-dimensional dividing network may include waveguides that differ inheight and/or width from the predetermined height and width of the feedwaveguides in order to achieve a desired taper profile.

In the present disclosure, feed waveguides that provide a signal toradiating elements may be divided between the top and bottom portions ofthe split block. Further, the feed waveguides may all be located in acommon plane where the midpoint of the height of feed waveguides iscommon for all of the feed waveguides. The three-dimensional dividingnetwork of waveguides may be located partly in the same plane as thefeed waveguides and partly in at least one other plane. For example, theentire height of a portion of the three-dimensional dividing network ofwaveguides may be machined into either the first or second portion ofthe split-block. When the two block pieces are brought together, asurface of the other block portion may form an edge of the portion orthe three-dimensional dividing network of waveguides that has its heightfully in one of the two block sections. In some examples, the verticalportion of these waveguide cavities and cuts are symmetric with respectto the split block seam.

In another example, the power dividing elements may be a two-dimensionaldividing network of waveguides. The two-dimensional dividing network ofwaveguides may use waveguide geometry to divide power. For example, thefeed waveguides may have a predetermined height and width. Thepredetermined height and width may be based on a frequency of operationof radar unit. The two-dimensional dividing network may includewaveguides that differ in width from the predetermined width of the feedwaveguides in order to achieve the desired taper profile. Thus, thedividing network may have a geometry that is varied compared to the feedwaveguide geometry.

In the present disclosure, the feed waveguides may be divided betweenthe top and bottom portions of the split block. Further, the feedwaveguides and the two-dimensional dividing network may all be locatedin a common plane where the midpoint of the height of feed waveguides iscommon for all of the feed waveguides. When the two block pieces arebrought together, the two half-height waveguide portions may couple andform a full-height waveguide.

In yet another example, the power dividing elements may be athree-dimensional dividing network of waveguides. The three-dimensionaldividing network of waveguides may form hybrid couplers to divide theelectromagnetic energy. In practice, the three-dimensional dividingnetwork may include waveguides that have a portion of the length of arespective waveguide adjacent to the length of a portion of anotherwaveguide. The waveguides may have adjacent short walls. The twowaveguides may be separated by a thin metal sheet. A coupling aperturemay be formed based on cutouts, holes, or spaces in the thin metal sheetto allow electromagnetic energy to couple from one waveguide to theadjacent waveguide.

Additionally, in a region that forms a short wall hybrid coupler, afull-height waveguide may be formed in a top block portion and afull-height waveguide may be formed in a bottom block portion. A thinmetal layer may be located at the seam between the two block portions toform both an edge of the respective waveguide of the dividing networkand a coupling aperture. Holes, cuts, perforations, or areas without thethin metal layer may form the aperture by which electromagnetic energymay couple from one waveguide of the dividing network to anotherwaveguide of the dividing network.

Both the three-dimensional dividing network of waveguides and thetwo-dimensional dividing network of waveguides presented herein allows apower dividing beamforming network to be constructed to be more compact(i.e. fit in a smaller volume) than traditional beamforming networks.Further, the three-dimensional dividing network and the two-dimensionaldividing network of waveguides presented herein may be constructed withreactive components. In practice, a reactive beam forming network mayavoid use of absorbing load elements. The use of reactive elementswithout absorbing load elements may enable the radar system to operatemore efficiently.

Further, the first metal layer may include a first half of the pluralityof wave-radiating channels, where respective wave-radiating channels maybe configured to receive the respective portions of electromagneticwaves from the wave-dividing channels, and where first halves of therespective wave-radiating channels include at least one wave-directingmember configured to propagate sub-portions of electromagnetic waves toanother metal layer.

Moreover, the second metal layer may include second halves of the inputwaveguide channel, the plurality of wave-dividing channels, and theplurality of wave-radiating channels. The second halves of therespective wave-radiating channels may include at least one pair ofoutput ports partially aligned with the at least one wave-directingmember and configured to radiate the sub-portions of electromagneticwaves propagated from the at least one wave-directing member out of thesecond metal layer. More particularly, a combination of a givenwave-directing member with a corresponding pair of output ports may takethe form of (and may be referred to herein as) a DOEWG, as describedabove.

While in this particular example the antenna includes multiplewave-dividing channels and multiple wave-radiating channels, in otherexamples the antenna may include, at a minimum, only a single channelconfigured to propagate all the electromagnetic waves received by theinput port to one or more wave-radiating channels. For instance, all theelectromagnetic waves may be radiated out of the second metal layer by asingle DOEWG. Other examples are possible as well.

Furthermore, while in this particular example, as well as in otherexamples described herein, the antenna apparatus may be comprised of twometal layers, it should be understood that in still other examples, oneor more of the channels described above may be formed into a singlemetal layer, or into more than two metal layers that make up theantenna. Still further, within examples herein, the concept ofelectromagnetic waves (or portions/sub-portions thereof) propagatingfrom one layer of a DOEWG antenna to another layer is described for thepurpose of illustrating functions of certain components of the antenna,such as the wave-directing members. In reality, electromagnetic wavesmay not be confined to any particular “half” of a channel during certainpoints of their propagation through the antenna. Rather, at thesecertain points, the electromagnetic waves may propagate freely throughboth halves of a given channel when the halves are combined to form thegiven channel.

In some embodiments discussed herein, the two metal layers may be joineddirectly, without the use of adhesives, dielectrics, or other materials,and without methods such as soldering, diffusion bonding, etc. that canbe used to join two metal layers. For example, the two metal layers maybe joined by making the two layers in physical contact without anyfurther means of coupling the layers.

In some examples, the present disclosure provides an integrated powerdivider and method by which each waveguide that feeds a plurality ofradiating doublets of a DOEWG may have its associated amplitudeadjusted. The amplitude may be adjusted based on a pre-defined taperprofile. Additionally, the present DOEWG may be implemented withoutcomplicated manufacturing process. For example, a Computerized NumericalControl (CNC) machining process may be implemented to make theabove-described adjustments in parameters such as height, depth,multiplicity of step-up or step-down phase adjustment components, etc.Yet further, the present disclosure may enable a much more accuratemethod of synthesizing a desired amplitude and phase to cause a realizedgain, sidelobe levels, and beam pointing for the antenna apparatus, ascompared to other types of designs.

Referring now to the figures, FIG. 1 is a flowchart of an example method100 to radiate electromagnetic energy. It should be understood thatother methods of operation not described herein are possible as well.

It should also be understood that a given application of such an antennamay determine appropriate dimensions and sizes for various machinedportions of the two metal layers described above (e.g., channel size,metal layer thickness, etc.) and/or for other machined (or non-machined)portions/components of the antenna described herein. For instance, asdiscussed above, some example radar systems may be configured to operateat an electromagnetic wave frequency of 77 GHz, which corresponds tomillimeter electromagnetic wave length. At this frequency, the channels,ports, etc. of an apparatus fabricated by way of method 100 may be ofgiven dimensions appropriated for the 77 GHz frequency. Other exampleantennas and antenna applications are possible as well.

Although the blocks are illustrated in a sequential order, these blocksmay also be performed in parallel, and/or in a different order thanthose described herein. Also, the various blocks may be combined intofewer blocks, divided into additional blocks, and/or removed based uponthe desired implementation.

Referring now to the figures, FIG. 1 is a flowchart of an example method100 to to radiate electromagnetic energy. It should be understood thatother methods of operation not described herein are possible as well.

Moreover, the method 100 of FIG. 1 will be described in conjunction withthe other Figures.

At block 102, the method 100 includes receiving electromagnetic energyfrom a source. The source may be a port (i.e. a through hole) in abottom metal layer. An electromagnetic signal may be coupled fromoutside the antenna unit into the waveguide through the source. Theelectromagnetic signal may come from a component located outside theantenna unit, such as a printed circuit board, another waveguide, orother signal source. In some examples, the source may be coupled toanother dividing network of waveguides

The electromagnetic energy may be received from a waveguide feed coupledto the waveguide. In one example, receiving electromagnetic energy by abeamforming network input of the waveguide may be performed via a portin a bottom layer and coupling the electromagnetic energy from the portinto the waveguide.

Additionally, the waveguide may be aligned on a plane defined by acenter of a width of the waveguide and a length of the waveguide. Forexample, and as discussed with respect to the following figures, thewaveguide may be constructed in a block. The waveguide and associatedbeamforming network may be created on a plane of the block defined by aseam of the block.

At block 104, the method 100 includes splitting the electromagneticenergy from the source as a divided signal among the plurality of feedwaveguides by a dividing network. The splitting may be performed with aset of dividers, such as a three-dimensional waveguide beam splitter.The beam splitter is configured to divide electromagnetic energy betweena plurality of radiating waveguides. The electromagnetic energy may bedivided based on a pre-determined taper profile. The taper profile maybe determined based on beam specifications for the transmitted beam. Forexample, a beam width and beam direction may be controlled based on thetaper profile. In some examples, the beam splitting may evenly dividethe electromagnetic energy between the plurality of feed waveguides. Inanother example, the beam splitting may output the electromagneticenergy between the plurality of feed waveguides with the respectiveelectromagnetic energy of the plurality of feed waveguides has equalphase.

At block 106, the method 100 includes for each of the plurality of feedwaveguides, adjusting a phase of the electromagnetic energy received byeach feed waveguide by the dividing network. The phase shifting may beperformed with a set of phase shifters, such as a three-dimensionalwaveguide beam splitter. The phase shifters are configured to adjust aphase of the divided electromagnetic energy for each of the plurality ofradiating waveguides. The divided electromagnetic energy may be phaseadjusted based on a pre-determined taper profile. As previouslydiscussed, the taper profile may be determined based on beamspecifications for the transmitted beam. For example, a beam width andbeam direction may be controlled based on the taper profile.

At block 108, the method 100 includes for each of the plurality of feedwaveguides, coupling electromagnetic energy to a plurality of radiatingelements coupled to the feed waveguide. In some examples, block 108includes coupling at least a portion of the electromagnetic energy fromthe waveguide to each one of a plurality of doublets. In some examples,the radiating elements may be singlets or other type of radiatingelements as well.

At block 110, the method 100 includes radiating electromagnetic energyby the plurality of radiating elements coupled to the plurality of feedwaveguides. The waveguide may have one or more radiating components. Theradiating components may take the form of antennas, slots, or otherradiating structures. During the transmission of signals, the radiatingcomponents are configured to convert guided electromagnetic energy frominside the waveguide to unguided electromagnetic energy radiated intofree space, such that the electromagnetic energy is transmitted by theradiating components. Notably, a radiating component may not transmitall the electromagnetic energy that is exposed to the respectiveradiating component. Based on both an impedance and polarization match,the radiating component may only transmit a portion of theelectromagnetic energy to which it is exposed. A portion of theelectromagnetic energy that is not radiated is reflected back into thewaveguide as reflected electromagnetic energy.

At block 112, the method 100 includes the splitting and adjusting beingbased in part on differences in the width between the waveguides of thedividing network and the feed waveguides. The two-dimensional waveguidemay be configured with reactive elements. The reactive elements may beformed by adjusting a width of at least one section of the waveguides ofthe dividing network. Reactive components may enable the dividingnetwork without using load elements to absorb some of the divided energyfrom the dividing network. By adjusting the width of various waveguidesections coupled to each of the feed waveguides, the desired amplitudeand phase of the taper profile for the feed waveguides may be achieved.Further, the two-dimensional waveguide may have a length in thex-dimension that is the same for each of the waveguide sections.

At block 114, the method 100 includes the dividing network being locatedin a common plane defined by the feed waveguides. In examples presentedherein, each of the feed waveguides may lie in a single plane. The planemay be defined by the seam of the split block construction waveguide.The two-dimensional dividing network may lie within the same plane. Byhaving some waveguide portions located within the top or bottom block ofthe split block, the dividing network may be made more compact thantraditional waveguide dividing networks.

Some components illustrated in of FIGS. 2A, 2B, and 2E are shown usingbroken lines, including elongated segments 204, second end 210, andpower dividers 214. The components shown in broken lines are describedherein with respect to the alignments shown in the respective figures.However, these components may have altered geometries and/or locationswithin the context of the disclosure. For example, the presentlydiscussed waveguide dividing networks as disclosed herein may replace aportion of the broken line components of FIGS. 2A, 2B, and 2E.

FIG. 2A illustrates an example first metal layer 200 including a firsthalf of a plurality of waveguide channels 202. These waveguide channels202 may comprise multiple elongated segments 204. At a first end 206 ofeach elongated segment 204 may be a plurality of collinearwave-directing members 208, each with sizes similar or different fromother wave-directing members. In line with the description above, thefirst ends 206 of the elongated segments 204 may be referred to hereinas a first half of wave-radiating channels.

At a second end 210 of the channels 202 opposite the first end 206, oneof the elongated segments 204 may include a through-hole 212 (i.e.,input port). A given amount of power may be used to feed a correspondingamount of electromagnetic waves (i.e., energy) into the apparatus, andthe through-hole 212 may be the location where these waves are fed intothe apparatus. In line with the description above, the singlechannel/segment of the waveguide channels 202 that includes the inputport may be referred to herein as an input waveguide channel.

Upon entering the apparatus, the electromagnetic waves may generallytravel in the +x direction, as shown, towards an array of power dividers214 (i.e., a “beam-forming network”). The array 214 may function todivide up the electromagnetic waves and propagate respective portions ofthe waves to respective first ends 206 of each elongated segment 204.More specifically, the waves may continue to propagate in the +xdirection after leaving the array 214 toward the wave-directing members208. In line with the description above, the array 214 section of thewaveguide channels may be referred to herein as wave-dividing channels.

As the portions of the electromagnetic waves reach the wave-directingmembers 208 at the first end 206 of each elongated segment 204 of thewaveguide channels 202, the wave-directing members 208 may propagatethrough respective sub-portions of the electromagnetic energy to asecond half of the waveguide channels (i.e., in the +z direction, asshown). For instance, the electromagnetic energy may first reach awave-directing member that is recessed, or machined further into thefirst metal layer 200 (i.e., a pocket). That recessed member may beconfigured to propagate a smaller fraction of the electromagnetic energythan each of the subsequent members further down the first end 206,which may be protruding members rather than recessed members. Further,each subsequent member may be configured to propagate a greater fractionof the electromagnetic waves travelling down that particular elongatedsegment 204 at the first end 206 than the member that came before it. Assuch, the member at the far end of the first end 206 may be configuredto propagate the highest fraction of electromagnetic waves. Eachwave-directing member 208 may take various shapes with variousdimensions. In other examples, more than one member (or none of themembers) may be recessed. Still other examples are possible as well. Inaddition, varying quantities of elongated segments are possible.

A second metal layer may contain a second half of the one or morewaveguide channels, where respective portions of the second half of theone or more waveguide channels include an elongated segmentsubstantially aligned with the elongated segment of the first half ofthe one or more waveguide channels and, at an end of the elongatedsegment, at least one pair of through-holes partially aligned with theat least one wave-directing member and configured to radiateelectromagnetic waves propagated from the at least one wave-directingmember out of the second metal layer.

Within examples, the elongated segment of the second half may beconsidered to substantially align with the elongated segment of thefirst half when the two segments are within a threshold distance, orwhen centers of the segments are within a threshold distance. Forinstance, if the centers of the two segments are within about ±0.051 mmof each other, the segment may be considered to be substantiallyaligned.

In another example, when the two halves are combined (i.e., when the twometal layers are joined together), edges of the segments may beconsidered to be substantially aligned if an edge of the first half of asegment and a corresponding edge of the second half of the segment arewithin about ±0.051 mm of each other.

In still other examples, when joining the two metal layers, one layermay be angled with respect to the other layer such that their sides arenot flush with one another. In such other examples, the two metallayers, and thus the two halves of the segments, may be considered to besubstantially aligned when this angle offset is less than about 0.5degrees.

In some embodiments, the at least one pair of through-holes may beperpendicular to the elongated segments of the second half of the one ormore waveguide channels. Further, respective pairs of the at least onepair of through-holes may include a first portion and a second portion.As such, a given pair of through-holes may meet at the first portion toform a single channel. That single channel may be configured to receiveat least the portion of electromagnetic waves that was propagated by acorresponding wave-directing member and propagate at least a portion ofelectromagnetic waves to the second portion. Still further, the secondportion may include two output ports configured as a doublet and may beconfigured to receive at least the portion of electromagnetic waves fromthe first portion of the pair of through-holes and propagate at leastthat portion of electromagnetic waves out of the two output ports.

FIG. 2B illustrates the second metal layer 220 described above. Thesecond metal layer 220 may include a second half of the plurality ofwaveguide channels 202 of the first metal layer 200 shown in FIG. 2A(i.e., a second half of the input waveguide channel, the wave-dividingchannels, and the wave-radiating channels). As shown, the second half ofthe waveguide channels 202 may take on the general form of the firsthalf of the channels, so as to facilitate proper alignment of the twohalves of the channels. The elongated segments of the second half 222may include second halves of the array of power dividers 224. Asdescribed above, electromagnetic waves may travel through the array 224,where they are divided into portions, and the portions then travel(i.e., in the +x direction, as shown) to respective ends 226 of thesecond halves of the elongated segments 222. Further, an end 226 of agiven elongated segment may include multiple pairs of through-holes 228,which may be at least partially aligned with the wave-directing members208 of the first metal layer 200. More specifically, each pair ofthrough-holes may be at least partially aligned with a correspondingwave-directing member, also referred to as a reflecting element, suchthat when a given sub-portion of electromagnetic waves are propagatedfrom the first metal layer 200 to the second metal layer 220, asdescribed above, those sub-portions are then radiated out of the pair ofthrough-holes (i.e., a pair of output ports) in the −z direction, asshown. Again, the combination of a given wave-directing member and acorresponding pair of output ports may form a DOEWG, as described above.

Moreover, a combination of all the DOEWGs may be referred to herein as aDOEWG array. In antenna theory, when an antenna has a larger radiatingaperture (i.e., how much surface area of the antenna radiates, where thesurface area includes the DOEWG array) that antenna may have higher gain(dB) and a narrower beam width. As such, in some embodiments, ahigher-gain antenna may include more channels (i.e., elongatedsegments), with more DOEWGs per channel. While the example antennaillustrated in FIGS. 2A and 2B may be suitable for autonomous-vehiclepurposes (e.g., six elongated segments, with five DOEWGs per segment),other embodiments may be possible as well, and such other embodimentsmay be designed/machined for various applications, including, but notlimited to, automotive radar.

For instance, in such other embodiments, an antenna may include aminimum of a single DOEWG. With this arrangement, the output ports mayradiate energy in all directions (i.e. low gain, wide beamwidth).Generally, an upper limit of segments/DOEWGs may be determined by a typeof metal used for the first and second metal layers. For example, metalthat has a high resistance may attenuate an electromagnetic wave as thatwave travels down a waveguide channel. As such, when a larger,highly-resistive antenna is designed (e.g., more channels, moresegments, more DOEWGs, etc.), energy that is injected into the antennavia the input port may be attenuated to an extent where not much energyis radiated out of the antenna. Therefore, in order to design a largerantenna, less resistive (and more conductive) metals may be used for thefirst and second metal layers. For instance, in embodiments describedherein, at least one of the first and second metal layers may bealuminum. Further, in other embodiments, at least one of the first andsecond metal layers may be copper, silver, or another conductivematerial. Further, aluminum metal layers may be plated with copper,silver, or other low-resistance/high-conductivity materials to increaseantenna performance. Other examples are possible as well.

The antenna may include at least one fastener configured to join thefirst metal layer to the second metal layer so as to align the firsthalf of the one or more waveguide channels with the second half of theone or more waveguide channels to form the one or more waveguidechannels (i.e., align the first half of the plurality of wave-dividingchannels with the second half of the plurality of wave-dividingchannels, and align the first half of the plurality of wave-radiatingchannels with the second half of the plurality of wave-radiatingchannels). To facilitate this in some embodiments, the first metallayer, a first plurality of through-holes (not shown in FIG. 2A) may beconfigured to house the at least one fastener. Additionally, in thesecond metal layer, a second plurality of through-holes (not shown inFIG. 2B) may be substantially aligned with the first plurality ofthrough-holes and configured to house the at least one fastener forjoining the second metal layer to the first metal layer. In suchembodiments, the at least one fastener may be provided into the alignedfirst and second pluralities of through-holes and secured in a mannersuch that the two metal layers are joined together.

In some examples, the at least one fastener may be multiple fasteners.Mechanical fasteners (and technology used to facilitate fastening) suchas screws and alignment pins may be used to join (e.g., screw) the twometal layers together. Further, in some examples, the two metal layersmay be joined directly to each other, with no adhesive layer in between.Still further, the two metal layers may be joined together using methodsdifferent than adhesion, such as diffusion bonding, soldering, brazing,and the like. However, it is possible that, in other examples, suchmethods may be used in addition to or alternative to any methods forjoining metal layers that are known or not yet known.

In some embodiments, one or more blind-holes may be formed into thefirst metal layer and/or into the second metal layer in addition to oralternative to the plurality of through-holes of the first and/or thesecond metal layer. In such embodiments, the one or more blind-holes maybe used for fastening (e.g., housing screws or alignment pins) or may beused for other purposes.

FIG. 2C illustrates an assembled view of an example antenna 240. Theexample antenna 240 may include the first metal layer 200 and the secondmetal layer 220. The second metal layer 220 may include a plurality ofholes 242 (through-holes and/or blind-holes) configured to housealignment pins, screws, and the like. The first metal layer 200 mayinclude a plurality of holes as well (not shown) that are aligned withthe holes 242 of the second metal layer 220. The two metal layers mayjoin at a common plane 230.

Further, FIG. 2C illustrates a DOEWG array 244 of a given width 246 anda given length 248, which may vary based on the number of DOEWGs andchannels of the antenna 240. For instance, in an example embodiment, theDOEWG array may have a width of about 11.43 mm and a length of about28.24 mm. Further, in such an example embodiment, these dimensions, inaddition to or alternative to other dimensions of the example antenna240, may be machined with no less than about a 0.51 mm error, though inother embodiments, more or less of an error may be required. Otherdimensions of the DOEWG array are possible as well.

In some embodiments, the first and second metal layers 200, 220 may bemachined from aluminum plates (e.g., about 6.35 mm stock). In suchembodiments, the first metal layer 200 may be at least 3 mm in thickness(e.g., about 5.84 mm to 6.86 mm). Further, the second metal layer 220may be machined from a 6.35 mm stock to a thickness of about 3.886 mm.Other thicknesses are possible as well.

In some embodiments, the joining of the two metal layers 200, 220 mayresult in an air gap or other discontinuity between mating surfaces ofthe two layers. In such embodiments, this gap or continuity should beproximate to (or perhaps as close as possible to) a center of the lengthof the antenna apparatus and may have a size of about 0.05 mm orsmaller.

FIG. 2D illustrates another assembled view of the example antenna 240.As shown, the first metal layer 200 may include a plurality of holes 250(through-holes and/or blind-holes) configured to house alignment pins,screws, and the like. One or more of the plurality of holes 250 may bealigned with the holes 242 of the second metal layer 220. Further, FIG.2D shows the input port 212, where the antenna 240 may receiveelectromagnetic waves into the one or more waveguide channels 202. Thetwo metal layers may join at a common plane 230.

FIG. 2E illustrates conceptual waveguide channels 260 formed inside anassembled example antenna. More particularly, the waveguide channels 260take the form of the waveguide channels 202 of FIGS. 2A and 2B. Forinstance, the channels 260 include an input port 262 to the inputwaveguide channel 264. The channels 260 also include wave-dividingchannels 266 and a plurality of radiating doublets 268 (i.e., a DOEWGarray). As described above, when electromagnetic waves enter thechannels 260 at the input port 262, they may travel in the +x directionthrough the input waveguide channel 264 and be divided into portions bythe wave-dividing channels 266 (e.g., by the power dividers). Thoseportions of electromagnetic waves may then travel in the +x direction torespective radiating doublets 268, where sub-portions of those portionsare radiated out each DOEWG through pairs of output ports, such as pair270, for instance.

In a particular wave-radiating channel, a portion of electromagneticwaves may first be propagated through a first DOEWG with a recessedwave-directing member 272 (i.e., an inverse step, or “well”), asdiscussed above. This recessed wave-directing member 272 may beconfigured to radiate the smallest fraction of energy of all the membersof the DOEWGs of the particular wave-radiating channel. In someexamples, subsequent wave-directing members 274 may be formed (e.g.,protruded, rather than recessed) such that each subsequent DOEWG canradiate a higher fraction of the remaining energy than the DOEWG thatcame before it. Phrased another way, each wave-directing member 272, 274may generally be formed as a “step cut” into a horizontal (+x direction)channel (i.e., a wave-radiating channel, or the “first end” of an“elongated segment” as noted above) and used by the antenna to tune theamount of energy that is radiated vs. the amount of energy that istransmitted further down the antenna.

In some embodiments, a given DOEWG may not be able to radiate more thana threshold level of energy and may not be able to radiate less than athreshold level of energy. These thresholds may vary based on thedimensions of the DOEWG components (e.g., the wave-directing member, ahorizontal channel, a vertical channel, a bridge between the two outputports, etc.), or may vary based on other factors associated with theantenna.

In some embodiments, the first and second metal layers may be machinedsuch that various sides of the waveguide channels 260 have roundededges, such as edge 276, 278, and 280, for example. Further shown inFIG. 2E are both attenuation ports 282 and attenuation components 284.The attenuation components 284 may be coupled to the attenuation ports282. And the attenuation ports 282 may be coupled to the elongatedsegments 222 of the wave-dividing channels 266. The design of theattenuation components 284 and attenuation ports 282 are discussedfurther with respect to FIG. 4B. In examples, where the beamforming(i.e. dividing network) is not completely reactive the attenuation ports282 may be used to removed electromagnetic energy from the waveguides.The attenuation ports 282 may couple electromagnetic energy toattenuation components 284 in order to absorb the undesiredelectromagnetic energy. Additionally, the dashed line 288 indicates thecommon plane of the feed waveguides.

FIG. 3A illustrates a network of wave-dividing channels 300 of anexample antenna, in accordance with an example embodiment. And FIG. 3Billustrates an alternate view of the network of wave-dividing channels300, in accordance with an example embodiment.

In some embodiments, the network (e.g., beam-forming network, as notedabove) of wave-dividing channels 300 may take the form of a tree ofpower dividers, as shown in FIG. 3A. Energy may enter the antennathrough the input waveguide channel and is divided (i.e., split) intosmaller portions of energy at each power divider, such as power divider302, and may be divided multiple times via subsequent power dividers sothat a respective amount of energy is fed into each of thewave-radiating channels (energy A-F, as shown). The amount of energythat is divided at a given power divider may be controlled by a powerdivision ratio (i.e., how much energy goes into one channel 304 versushow much energy goes into another channel 306 after the division). Agiven power division ratio may be adjusted based on the dimensions ofthe corresponding power divider. Further, each power divider andassociated power division ratio may be designed/calculated in order toachieve a desired “power taper” at the wave-radiating channels. In sucha case, the antenna may be designed with a “Taylor window” (e.g.,radiation ripples drop off at edges) or other window such that sidelobesof the antenna's far-field radiation pattern may be low. As an example,the power division ratios of the power dividers may be set such thatenergy portions A, B, C, D, E, and F are approximately 3.2%, 15.1%,31.7%, 31.7%, 15.1%, 3.2% of the energy, respectively. Other examplepower divisions are possible as well.

Within examples, a technique for dividing energy between two channels304, 306 may be to use a structure of channels (e.g., a four-portbranchline coupler) such as that shown at the bottom of FIG. 3A. Such atechnique and structure design may include a “terminator” 308 at the endof a channel, as shown in FIGS. 3A and 3B, where small wedges of radiofrequency-absorbing material may be located to absorb energy thatreturns backwards through the channel to that terminator 308. Theterminator may also be the absorption component of FIG. 2E.

FIG. 4A illustrates an example two-dimensional beamforming network, inaccordance with an example embodiment. The two-dimensional beamformingnetwork has two main components. The two-dimensional beamforming networkincludes a waveguide input 402, a power dividing section 404, and aphase adjusting section 406. The two-dimensional beamforming network maybe located in the same plane of the split block construction as the feedwaveguides.

The two-dimensional beamforming network of FIG. 4A may include onlyreactive components. As previously discussed, the use of reactivecomponents may eliminate the need for beamforming network to includeabsorption components that were previously discussed.

The two-dimensional beamforming network may receive electromagneticenergy at the waveguide input 402, ends 408A-408D may be shorts. Thereceived electromagnetic energy may be divided by the power dividingsection 404. The power dividing section 404 may divide theelectromagnetic energy as divided electromagnetic energy based on apredetermined taper profile. The divided electromagnetic energy may haveits phase adjusted by the phase adjusting section 406. The phaseadjustment provided by of each respective phase adjusting trombonessections (406A-406F) in splitting section 406 may also be defined basedon the taper profile. As shown in FIG. 4A, a portion of the waveguidesof the phase adjusting section 406 may have a width that is differentthan the widths of the feed waveguides. Further, the waveguides of phaseadjusting section 406 may be folded so each respective phase adjustingsection 406 occupies the same physical length in the x direction.

The power dividing elements of FIG. 4A are a two-dimensional dividingnetwork of waveguides. The two-dimensional dividing network ofwaveguides use waveguide geometry to divide power with no changes to thethickness of the waveguide A dimension. As previously discussed, thefeed waveguides may have a predetermined height and width. Thepredetermined height and width may be based on a frequency of operationof radar unit. The two-dimensional dividing network may includewaveguides 406A-406F that differ in width from the predetermined width(i.e. the N dimension) of the feed waveguides in order to achieve thedesired taper profile. By adjusting the waveguide widths, both the phaseand and amplitude of the splitting of the electromagnetic energy may becontrolled. Thus, the dividing network may have a geometry that isvaried compared to the feed waveguide geometry.

In the present disclosure, the feed waveguides may be divided betweenthe top and bottom portions of the split block. Further, the feedwaveguides and the two-dimensional dividing network may all be locatedin a common plane 410 where the midpoint of the height of feedwaveguides is common for all of the feed waveguides. When the two blockpieces are brought together, the two half-height waveguide portions maycouple and form a full-height waveguide.

FIG. 4B illustrates an example three-dimensional beamforming network, inaccordance with an example embodiment. The three-dimensional beamformingnetwork has three main components. The three-dimensional beamformingnetwork includes a waveguide input 422, a power dividing section 424, aphase adjusting section 426 (i.e. a three dimensional phase adjustinglens). The three-dimensional beamforming network may not be completelylocated in the same plane of the split block construction as the feedwaveguides.

The three-dimensional beamforming network of FIG. 4B may include onlyreactive components. As previously discussed, the use of reactivecomponents may enable the beamforming network to not need the absorptioncomponents that were previously discussed.

The three-dimensional beamforming network may receive electromagneticenergy at the waveguide input 422, ends 428A-428D may be shorts. Thereceived electromagnetic energy may be divided by the three dimensionalpower dividing section 424. The power dividing section 424 may dividethe electromagnetic energy as divided electromagnetic energy based on apredetermined taper profile. The divided electromagnetic energy may haveits phase adjusted by the phase adjusting (three dimensional phaseadjusting lens) section 426. The phase adjustment provided by of eachrespective phase adjusting section 426 may be achieved by theadjustments of heights (i.e. the A dimension) of the waveguide sections,without any changes to widths (i.e. the B dimension) may also be definedbased on the taper profile. The output of the phase adjustment section426 may be coupled to the feed waveguides as shown in FIG. 4C.

The power dividing elements of FIG. 4B of the DOEWG antenna are athree-dimensional dividing network of waveguides. Similar to thetwo-dimensional waveguide of FIG. 4A, the three-dimensional dividingnetwork of waveguides may use waveguide geometry to divide power. Thepredetermined height and width of the feed waveguides may be based on afrequency of operation of the radar unit. The three-dimensional dividingnetwork may include waveguides that differ in height and width from thepredetermined height and width of the feed waveguides in order toachieve the desired taper profile. For example, waveguide 428A and 428Bare shown having a different height.

As discussed above, the three-dimensional dividing network of waveguidesmay be located partly in the common plane 430 as the feed waveguides andpartly in at least one other plane. For example, the entire height of aportion of the three-dimensional dividing network of waveguides may bemachined into either the first or second portion of the split-block.When the two block pieces are brought together, a surface of the otherblock portion may form an edge of the portion or the three-dimensionaldividing network of waveguides that has its height fully in one of thetwo block sections.

FIG. 4C illustrates an example three-dimensional beamforming network, inaccordance with an example embodiment. The three-dimensional beamformingnetwork of FIG. 4C may operate in a similar manner to the previouslydescribed beamforming network of FIG. 4B. The three-dimensionalbeamforming network includes a waveguide input 442, a power dividingsection 444, and a phase adjusting section 446. The three-dimensionalbeamforming network may not be completely located in the common plane449 of the split block construction as the feed waveguides.Additionally, FIG. 4C shows the radiating section 448 that includes thefeed waveguides and the radiating elements. Further, waveguide 448A and448B are shown having a different height.

FIG. 4D illustrates another example three-dimensional unfoldedbeamforming network 450 with short wall coupling elements, designated intwo examples as 454A and 454B, typically shown as one in the inputdesignated as 452A, in accordance with an example embodiment.Additionally, FIG. 4E illustrates an example three-dimensional foldedbeamforming network 460 (i.e. a folded version of FIG. 4D) with shortwall coupling, designated in two examples as 464A and 464B, inaccordance with an example embodiment. This version may be much shorter(in the x-direction) than the unfolded version of FIG. 4D, and may useabsorbtion load elements to provide termination on the a PCB. Thethree-dimensional folded beamforming network with short wall coupling450 and 460 may not use exclusively reactive elements. Thus, thethree-dimensional beamforming network with short wall coupling 450 and460 may use the previously-discussed absorption components.Additionally, the power division and phase shifting may be based on apredetermined taper profile (as previously discussed). Additionally, thewaveguides that form a three-dimensional beamforming network with shortwall coupling 450 and 460 may not all be located in the plane defined bythe feed waveguides (the plane is defined by 452 and 462 respectively).

The dividing and phase shifting provided by three-dimensionalbeamforming network with short wall coupling 450 and 460 may beperformed based on two stacked waveguide sections having short wallsections that are adjacent to each other. When the short walls areadjacent to each other, they may be separated by a thin metal layer toprovide the coupling apertures.

The separation metal layer may be a thin metal layer. The thin metallayer may include a coupling aperture (discussed further with respect toFIG. 4F). The coupling aperture may enable electromagnetic energy tocouple from one waveguide section into another waveguide section that iscoupled to the short walls. In some examples, one waveguide may beformed in a top block of the split block and the other waveguide may beformed in a bottom block of the split block. The thin metal layer may belocated between the two block sections. The three-dimensionalbeamforming network with short wall coupling 450 and 460 may also have aramp section. The ramp section may couple a section of waveguide that isnot in the common plane of the feed waveguides into the common plane ofthe feed waveguides. In another example, the ramp section (shown as 482of FIG. 4F) may couple two adjacent sections of waveguide that are notin the common plane of the feed waveguides into the common plane of thefeed waveguides (shown as 480 of FIG. 4F).

The power dividing elements of FIG. 4D of the DOEWG antenna are athree-dimensional dividing network of waveguides. The three-dimensionaldividing network of waveguides may form hybrid couplers to divide theelectromagnetic energy. As previously discussed, the three-dimensionaldividing network may include waveguides that have a portion of thelength of a respective waveguide adjacent to the length of a portion ofanother waveguide. The waveguides may have adjacent short walls. The twowaveguides may be separated by a thin metal sheet. The coupling aperturemay be formed based on cutouts, holes, or spaces in the thin metal sheetthat allows electromagnetic energy to couple from one waveguide to theadjacent waveguide.

Additionally, in a region that forms a short wall hybrid coupler, afull-height waveguide may be formed in a top block portion and afull-height waveguide may be formed in a bottom block portion. A thinmetal layer may be located at the seam between the two block portions toform both an edge of the respective waveguide of the dividing networkand a coupling aperture. Holes, cuts, perforations, or areas without thethin metal layer may form the aperture by which electromagnetic energymay couple from one waveguide of the dividing network to anotherwaveguide of the dividing network.

FIG. 4F illustrates an example short wall coupler, in accordance with anexample embodiment. The short wall coupler may function in a similarmanner to branch line coupler of FIG. 3A. However, the short wallcoupler is formed between two sections that are aligned verticallyadjacent to each other or can be thought as stacked one on top ofanother with the shared short wall being a thin metal sheet.

Energy may enter the antenna through an input waveguide channel and isdivided (i.e., split) into smaller portions of energy at each powerdivider, such as power divider 470, and may be divided multiple timesvia subsequent power dividers so that a respective amount of energy isfed into each of the feed waveguides. The amount of energy that isdivided at a given power divider may be controlled by a power divisionratio (i.e., how much energy goes into one channel 304 versus how muchenergy goes into another channel 306 after the division). A given powerdivision ratio may be adjusted based on the dimensions of thecorresponding power divider. Further, as previously discussed each powerdivider and associated power division ratio may be designed/calculatedin order to achieve a desired “power taper” at the wave-radiatingchannels.

Within examples, (such as that shown in FIG. 4F) a technique fordividing energy between two vertically adjacent waveguides 474, 476 maybe to use a thin metal layer with a coupling aperture 472 such as thatshown in FIG. 4F. Such a technique and structure design may include anabsorption component such as the terminator the end of a channel, asshown in FIGS. 3A and 3B, or the absorption component of FIG. 2E. Byadjusting the size, shape, and location of the coupling aperture 472,the desired taper profile may be achieved. Further, two adjacentwaveguides, each located in a different split block section may coupleto ramp section 482 to form a single waveguide. The single waveguideafter the ramp section may be located in the common plane of the splitblock.

It should be understood that other shapes and dimensions of thewaveguide channels, portions of the waveguide channels, sides of thewaveguide channels, wave-directing members, and the like are possible aswell. In some embodiments, a rectangular shape of waveguide channels maybe highly convenient to manufacture, though other methods known or notyet known may be implemented to manufacture waveguide channels withequal or even greater convenience.

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g. machines,apparatuses, interfaces, functions, orders, and groupings of functions,etc.) can be used instead, and some elements may be omitted altogetheraccording to the desired results. Further, many of the elements that aredescribed are functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the scope beingindicated by the following claims.

What is claimed is:
 1. A radar system comprising: a plurality of feedwaveguides, wherein each feed waveguide is configured to guideelectromagnetic energy to at least one radiating element, and whereinthe plurality of feed waveguides is arranged such that centers of theheights of the feed waveguides are located in a common plane; and aplurality of waveguides arranged as a dividing network, wherein thedividing network is configured to: receive electromagnetic energy from asource, split the electromagnetic energy from the source among theplurality of feed waveguides, such that each feed waveguide receives arespective portion of the electromagnetic energy from the source,wherein the splitting is based in part based on differences in widthbetween the waveguides of the dividing network and the feed waveguides,and wherein a taper profile specifies an amplitude for each feedwaveguide; and wherein the dividing network of waveguides is located inthe common plane of the feed waveguides.
 2. The radar system accordingto claim 1, wherein the dividing network comprises reactive elements andno absorption load elements.
 3. The radar system according to claim 1,wherein the radar system is manufactured using a split-blockconstruction.
 4. The radar system according to claim 3, wherein a seamof the split-block is at the center of the height of the feedwaveguides.
 5. The radar system according to claim 3, wherein a seam ofthe split-block is at the center of the height of the dividing networkof waveguides.
 6. The radar system according to claim 1, wherein thedividing network is further configured to: adjust a phase of theelectromagnetic energy received by each waveguide; and wherein theadjusting is based in part based on differences in width between thewaveguides of the dividing network and the feed waveguides, and whereinthe taper profile further specifies a phase for each feed waveguide. 7.The radar system according to claim 1, wherein the dividing network isconfigured to split the electromagnetic energy based on an amplitude anda phase of the taper profile.
 8. The radar system according to claim 7,wherein the taper profile is selected based on a desired radiationpattern for the radar system.
 9. The radar system according to claim 1,wherein a power splitting section of the dividing network is furtherconfigured to evenly split the electromagnetic energy from the sourceamong the plurality of feed waveguides.
 10. The radar system accordingto claim 9, wherein the power splitting section is configured to outputa plurality of divided signals, each having approximately the sameamplitude and phase of each other divided signal.
 11. The radar systemaccording to claim 10, wherein a phase adjusting section of the dividingnetwork is further configured to adjust the phase of each respectivedivided signal based on a predetermined phase shift for each respectivedivided signal.
 12. A method of radiating a radar signal comprising:receiving electromagnetic energy from a source; splitting theelectromagnetic energy from the source as a divided signal among aplurality of feed waveguides by a dividing network, such that each feedwaveguide receives a respective portion of the electromagnetic energyfrom the source; for each of the plurality of feed waveguides, couplingelectromagnetic energy to at least one radiating element coupled to thefeed waveguide; and radiating electromagnetic energy by the at least oneradiating element coupled to the plurality of feed waveguides; whereinthe splitting is based in part based on differences in width between thewaveguides of the dividing network and the feed waveguides, and whereinthe dividing network of waveguides is located in a common plane of thefeed waveguides.
 13. The method according to claim 12, wherein each ofthe divided signals have approximately the same amplitude as each otherdivided signal.
 14. The method according to claim 13, wherein each ofthe divided signals have approximately a same phase as each otherdivided signal.
 15. The method according to claim 12, wherein thesplitting is performed by reactive elements and no absorption loadelements.
 16. The method according to claim 12, wherein each feedwaveguide is further configured to conduct electromagnetic energy fromthe dividing network to the at least one radiating element, wherein theconducted electromagnetic energy has approximately zero current at aseam of a split-block.
 17. The method according to claim 16, wherein theseam of the split-block is at the center of the height of the feedwaveguides.
 18. The method according to claim 16, further comprisingadjusting a phase of each divided signal based on a predetermined phaseshift for each respective divided signal.
 19. A waveguide systemcomprising: a plurality of feed waveguides located in a common planehaving a common height, each feed waveguide configured to guideelectromagnetic energy from an end of the feed waveguide to at least oneradiating element coupled to the feed waveguide; a waveguide source; adividing network comprising a plurality of waveguides, wherein thedividing network is located in the common plane and has the commonheight, wherein the dividing network is configured to: receiveelectromagnetic energy from the source, split the electromagnetic energyfrom the source among the plurality of feed waveguides, such that eachfeed waveguide receives a respective portion of the electromagneticenergy from the source, and wherein the splitting is based in part basedon differences in width between the waveguides of the dividing networkand the feed waveguides, and wherein the dividing network comprisesreactive elements and no absorption load elements.
 20. The waveguidesystem of claim 19, wherein the waveguide system is manufactured using asplit-block construction, and wherein the seam of the split-block is ata location of the waveguide having approximately zero current.